Medical or nondestructive testing (NDT) ultrasound imaging applications have a growing demand for more sophisticated transmit-pulse/echo-signal switching in the receiver frontend circuit. This may be necessary to generate high resolution acoustic images. The conventional ultrasound T/R echo switching circuits usually have an array of high-voltage diode switches or MOSFET-based voltage-controlled switch devices in between a transducer probe PZT array and Tx/Rx channel circuitry
These circuits have several limitations. These circuits ether are require to have the forward bias current from two low-noise, very clean power supplies for the diode-bridge type of T/R switch, or have a quite larger size MOSFET analog switch with control circuit for the MOSFET-based type of T/R switch, which normally has higher turn-off trig voltage or current, and higher off-capacitance intrinsically. Second, the transmitting pulses are generally high voltage and the receiving echo signals are generally low voltage. However, both signals have to apply to the same T/R switch. This requires that every T/R switch must have a low on-impedance when the T/R switch is turned on, and that it can withstand high voltage when it is turned off. In order to have low on-resistance in the diode-bridge type circuit normally requires quite large forward bias current (e.g., 5 to 10 mA). Further, in a 128-channel system total power of 6.4 to 12.8 Watts of clean power supplies and 256 pieces of decoupling capacitors are also required. Additional PCB area is also required too for all these circuitry. These requirements make the cost of the T/R switch very high.
Therefore, it would be desirable to provide a circuit and method that overcomes the above problems. The circuit and method would be able to switch the echo signal to overcome the above problems.